"How can you raise a pin to a higher note?" said I. "Hammer her down farther," said he. "And to make a lower note?" I asked. "Pull her up a little," said he. "How do you manage the time?" "Oh, when you want to go slow, you put the pins a good ways apart; and when you want to go fast, you plant 'em thicker." The next day I found that this ridiculous brother of mine had set up a pin-organ in a circular form. He had made one of those little whirligigs which spin around when they are held over the register or by a stove-pipe, and then had connected it by a string with a wheel. This wheel, as it turned, set an upright shaft in motion, and from this there projected a stick armed at the end with a pin. This was arranged, as is shown in the cut, so that when it revolved, the pin in the stick played upon the pins in the circle, and rattled off the "Mulligan Guards" at a tremendous pace. [Illustration: THE PIN-ORGAN.] Johnny says that he invented the circular arrangement, and that all the boys he knows are making these pin-organs for themselves, which I am not at all surprised to hear. ABOUT THE PORPOISES. BY J. D. The porpoise is a long, sleek fish without scales, black on the back, and white and gray beneath. He is from four to ten feet in length, and his sociability and good-nature are proverbial among seamen of all nations. A porpoise is rarely seen alone, and if he by chance wanders from his friends, he acts in a very bewildered and foolish manner, and will gladly follow a steamer at full speed rather than be left alone. He is a very inquisitive fish, and is always thrusting his funny-looking snout into every nook that promises diversion or sport. [Illustration: A SCHOOL OF PORPOISES.] A very familiar spectacle at sea is a school of porpoises--or "porpusses," as the sailors call them. As soon as a school catches sight of a ship, they immediately make a frantic rush for it, as if their life depended upon giving it a speedy welcome. After diving under the vessel a few times to inspect it and try its speed, they take their station under the bows, just ahead, and proceed to cut up every antic that a fish is capable of. They jump, turn over, play "leap-frog" and "tag" in the most approved fashion. Their favorite antic is to dive a few feet and then come to the surface, showing their backs in a half circle, and then, making a sound like a long-drawn sigh, disappear again. Sailors call them "sea-clowns," and never allow them to be harmed. They are met with in schools of from two or three to thousands. They often get embayed in the inlets and shallow rivers which their curiosity leads them to investigate. A porpoise once came into the Harlem River and wandered up and down for a week seeking a way out. One day he suddenly made his appearance amid some bathers and scattered them by his gambols.